There are a number of interesting devices which have been designed to measure both angular rate and linear acceleration from a single instrument. One company has developed a Spin Coupled Accelerometer Gyro. This spin coupling technique employs a non-orthogonal suspension coupling of the rotor to the shaft, resulting in a specific mechanical coupling between the normal rotor motions about one of the rotating axes normal to the shaft and the shaft axis. The instrument is designed to be sensitive only to the sum of angular rate and linear acceleration inputs. The complexity of the Spin Coupled Accelerometer Gyro design results in a relatively expensive instrument. Another company has designed a multifunction sensor which makes use of a ballbearing rotor which carries piezoelectric acceleration transducers. This design, although relatively low in cost, suffers some from twice spin frequency bearing noise.
The simplicity of the present invention results in an instrument that is low in cost and the air bearing suspension results in an instrument that does not suffer from twice spin frequency bearing noise.